According to the present invention, a thickness detection sensor unit (52) comprises: a reference roller (110); a displaceable displacement roller (210); a lever (220) that moves according to displacement of the displacement roller (210); a displacement amount detection unit (230) for detecting the displacement amount of the displacement roller (210); and a vibration damping unit (300) that applies a frictional force to the lever (220) when the lever (220) moves. The vibration damping unit (300) applies a relatively large frictional force to the lever (220) when the lever (220) moves in a first direction in which the displacement roller (210) moves away from the reference roller (110), and applies a relatively small frictional force to the lever (220) when the lever (220) moves in a second direction in which the displacement roller (210) approaches the reference roller (110).